evening on both of our coasts tonight. on the west coast in southern california, a nerve-racking and disconcerting day after three murders, two more people wounded and the word from police that one of their own, be an ex police officer, a military veteran, is targeting police officers. as a result, law enforcement there on a hair-trigger, and the state has been on alert all day. right now as we look live, the search is focused on the big bear ski area, bear mountain, in southern california. now, on the east coast, preparations are under way for a potentially history-making snowstorm. along the eastern seaboard on up to new england, it's happening the way the worst of the storms happen. two systems coming together, joining forces, blizzard warnings are posted across a wide area. 50 million americans in the path of this one before it's all over. it's where we begin tonight. meteorologist jim cantore of the weather channel is in boston. nbc's ron mott in mass. we begin there. ron, good evening. >> reporter: brian, good evening to you. a big rush on this story earlier today.